The oligosaccharide moiety of glycoconjugates is increasingly believed to play an important role in influencing biological activities and cellular recognition phenomena in health and disease. However, much remains to be elucidated concerning the synthesis and cellular expression of glycoconjugates. The proposed studies will employ immunocytochemical techniques to investigate the subcompartmental organization of glycosylation reactions within the Golgi apparatus. The proposed work is divided into three experimental sections: 1) The subcompartmental distribution of beta1,4 galactosyltransferase in the Golgi apparatus of several different bovine epithelial cells will be investigated. Although this enzyme has been localized in other cell types, the results have recently been challenged due to questions of antibody specificity. We will use two well characterized monoclonal antibodies known to bind to only protein epitopes of galactosyltransferase, to determine the restricted distribution of this enzyme in the Golgi apparatus of different epithelial cell types from various organs. 2) Immunocytochemical localization of two sets of two sequentially-acting terminal glycosyltransferases. These independent double labeling experiments will determine the Golgi apparatus distribution of beta1,4 galactosyltransferase with alpha2,6 sialytransferase, and beta1,4 galactosyltransferase with alpha1,3 galactosyltransferase. The aim of this portion of the study is to determine whether two sequentially acting terminal glycosyltransferases are housed in identical or different Golgi apparatus subcompartments (i.e. trans cisternae versus trans Golgi network). 3) Immunocytochemical localization of CMP-sialic acid: lactosylceramide alpha2,3 sialytransferase in rat hepatocytes. Sections 1 and 2 described above investigate Golgi apparatus subcompartmentation of glycosyltransferases involved with modification of glycoproteins. Section 3 will involve the localization for the first time of a glycosyltransferase involved in the modification of glycolipids. These studies will serve to further define the subcompartmental organization in the Golgi apparatus of glycosyltransferases involved in the modification of both glycoproteins and glycolipids.